1. Technical Field
The present invention relates to a display device for a computer system, and more particularly, to an automatic contrast control mechanism for a display device using a detected distance between a user and the front panel of the display device to control the display contrast automatically.
2. Background Art
Conventional display device, both color and monochrome, typically has built-in control inputs for user adjustments of display parameters such as contrast, brightness, picture position including horizontal and vertical positioning, size, tint, color balance, focus, inter alia. Multi frequency display device includes several control inputs which increase the number of combinations of adjustments that a user can made. These control inputs may be remotely controlled or mounted at different locations of the display device where the user may open to access the controls as determined by each manufacturer.
For cathode-ray tube (CRT) device, the control inputs for contrast and brightness typically interact with video circuitry in the display device, and modulate the signal by varying electrical potential that effect the formation of an on-screen image. The brightness control, for example, adjusts the level of the scanning electron beam, which in turn makes the on-screen image brighter or less bright. Contrast is the linear relationship between incoming video dot data signal strength and the current screen brightness. In addition to brightness and contrast control inputs, there are also control inputs for position and sizing, which allow the user to alter the position of the display on the screen and to adjust the height and width of the display area on the screen. Exemplars of contemporary display device with control inputs are disclosed in U.S. Pat. No. 5,550,556 for Transmitting Data And Commands To Display Monitors issued to Wu et al., U.S. Pat. No. 5,532,719 for Remote Control Of Display Functions issued to Kikinis, U.S. Pat. No. 5,488,434 for Picture Adjusting Method Of A Color Television And Its Circuit issued to Jung, and U.S. Pat. No. 5,457,473 for Image Display Apparatus issued to Arai et al. When the control inputs such as picture contrast or brightness are executed, however, the picture contrast or brightness levels are fixed until further adjustments are manually requested by the user.
Contemporary display device with such control inputs, as I have observed, seldom takes into account the user's close proximity to the display screen and the duration of such a proximity. Consequently, if the user spends long hours in close proximity of such display device, particularly in CAD/CAM applications, there is no mechanism provided to alleviate the user's eye strain.